The role of a memory system is twofold. It provides reliable and consistent data storage and quick responses to read and write requests of processors and input/output (I/O) devices. Most memory systems include a plurality of memory devices such as dynamic random access memories (DRAMs), synchronous direct random access memories (SDRAMs), or other memory devices.
The Dual In-Line Memory Module (DIMM) has become an industry standard memory packaging design. DIMMs are small printed circuit boards mounted with a plurality of memory devices. DIMMs have 168 pins and can transfer 64 bits at a time. DIMMs have leads accessible via both sides of a printed circuit board's electrical connector unlike its predecessor, the Single In-Line Memory Module (SIMM), which has leads on only one side of the printed circuit board's electrical connector. DIMMs are inserted into small socket connectors that are soldered onto a larger printed circuit board, or motherboard. Because DIMMs are socketed, they are inherently replaceable and upgradeable.
Typically, a memory system in a computer system includes a plurality of DIMMs. The DIMMs are coupled in parallel to a memory bus having address, data, and control lines. The memory bus is routed onto each DIMM and to each of the plurality of memory devices mounted on each of the DIMM. The memory devices are connected in parallel via the memory bus.